Redline MT90 75W90 GL-4 Synthetic Gear Oil (50304)

Red Line Oil
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MT90 75W90 GL-4 Full Synthetic Gear Oil by Red Line

Since most GL-5 gear oils for differentials are too slippery for manual transmissions, Red Line offers these products that ensure proper shifting while providing ultimate wear protection. Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota, Mendeola transmissions and Atlas transfer cases for Off Road.


  • Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)
  • Red Line offers lubricants to pinpoint nearly every transmission application
  • Excellent gear and synchro protection, balanced slipperiness for easier shifting in cold climates
  • Excellent for high- and low-mile transmissions
  • Compatible with petroleums and other synthetics

MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears. Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specified. Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40


  • Universal


  • API Service Class: GL-4
  • SAE Viscosity Grade: 75W90
  • Vis @ 100°C: 15.6
  • Vis @ 40°C: 86.2
  • Viscosity Index: 194
  • Pour Point, °C: -45
  • Pour Point, °F: -49
  • Brookfield Viscosity @ -40°C, Poise: 320

What's In The Box?

  • 1 Quart/Gallon - Red Line MT90 75W90 GL4 Gear Oil



  • Manufacturer Standard Warranty

Customer Reviews

Based on 3 reviews
Zakariyya Khan
Does wonders for my synchros!

Ive been running Redline in both my drift cars for over 5 years now. Ive got to say it really reduces grinding and makes the tranny quieter and alot smoother. And although it doesnt last as long as the cheaper regular fluids, its definitely worth the upgrade. Nothing but praise for this product, Ive been faithfully using redline products for a while now, and I dont think Im going to stop anytime soon.

Shane G
Great for Transmission with Brass Synchro's

Smooth shifts in our BMW Getrag 260 Transmission, lower operating temps and safe for soft metal synchro's. The sulphur found in most GL-5 fluids will start to eat away the soft metals (brass synchros).
This fluid works perfect for our BMW E30 endurance racecar. Good stuff

Josh Thompson
Great fluid

One of the only fluids I’ll use in the evo drivetrain